* {
    margin: 0;
    padding: 0;
    list-style: none;
    outline: none;
    text-decoration: none;
    color: #333333;
    font-family: "Microsoft YaHei";
}

img {
    border: none;
}

/*给父级容器添加伪类*/
.clear::after {
    content: ".";
    clear: both;
    display: block;
    height: 0;
    overflow: hidden;
    visibility: hidden;
}